Maximum Frequency of LEDs

Discussion in 'General Electronics Chat' started by Willen, May 24, 2019.

  1. Willen

    Thread Starter Member

    Nov 13, 2015
    283
    31
    Hi,
    A basic question: transistors, diodes has maximum frequency rating. 1n4007 are slow, 1n5819 are fast and 1n34 are ultra fast diodes. What happens if I fed UHF signal to an ordinary LED? Does that glow? How much rectified voltage I get if I fed UHF 5V signal in a 1n4007?

    Answer of these question helps me to make concept about diodes' frequency.
     
  2. nsaspook

    AAC Fanatic!

    Aug 27, 2009
    5,939
    6,711
    The junction switching speed (forward/reverse recovery time) and device (internal) capacitance are major factors. Large power diodes are slow because there is more to move when the voltage polarity reverses. At UHF a diode with a large junction capacitance provides a short-cut across the junction taking the diode mainly out of the circuit in actual operation. This capacitance changes with the value of reverse voltage so it can be useful. Varicap
    [​IMG]

    http://web.iitd.ac.in/~shouri/eel201/tuts/diode_switch.pdf
     
    Willen likes this.
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